Two-Dimensional RC/SW Constrained Codes: Bounded Weight and Almost Balanced Weight

In this work, we study two types of constraints on two-dimensional binary arrays. Given $p\in [{0,1}],\epsilon \in [{0,1/2}]$ , we study 1) the $p$ -bounded constraint: a binary vector of size $n$ is said to be $p$ -bounded if its weight is at most $pn$ , and 2) the $\epsilon $ -balanced constraint: a binary vector of size $n$ is said to be $\epsilon $ -balanced if its weight is within $\big [(1/2-\epsilon)n, (1/2+\epsilon)n\big]$ . Such constraints are crucial in several data storage systems, those regard the information data as two-dimensional (2D) instead of one-dimensional (1D), such as the crossbar resistive memory arrays and the holographic data storage. In this work, efficient encoding/decoding algorithms are presented for binary arrays so that the weight constraint (either $p$ -bounded constraint or $\epsilon $ -balanced constraint) is enforced over every row and every column, regarded as 2D row-column (RC) constrained codes; or over every window (where each window refers to as a subarray consisting of consecutive rows and consecutive columns), regarded as 2D sliding-window (SW) constrained codes. While low-complexity designs have been proposed in the literature, mostly focusing on 2D RC constrained codes where $p=1/2$ and $\epsilon =0$ , this work provides efficient coding methods that work for both 2D RC constrained codes and 2D SW constrained codes, and more importantly, the methods are applicable for arbitrary values of $p$ and $\epsilon $ . Furthermore, for certain values of $p$ and $\epsilon $ , we show that, for sufficiently large array size, there exists linear-time encoding/decoding algorithm that incurs at most one redundant bit.